物理化学学报 >> 2009, Vol. 25 >> Issue (06): 1136-1142.doi: 10.3866/PKU.WHXB20090630

研究论文 上一篇    下一篇

Beta分子筛中Al的分布和Brφnsted酸的酸性强度

孙秀良, 黄崇品, 张傑, 陈标华   

  1. 北京化工大学化工资源有效利用国家重点实验室, 北京 100029
  • 收稿日期:2009-01-13 修回日期:2009-03-14 发布日期:2009-06-05
  • 通讯作者: 黄崇品 E-mail:huangcp@mail.buct.edu.cn

Location of Al and Acid Strength of Brφnsted Acid in Beta Zeolite

SUN Xiu-Liang, HUANG Chong-Pin, ZHANG Jie, CHEN Biao-Hua   

  1. State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, P. R. China
  • Received:2009-01-13 Revised:2009-03-14 Published:2009-06-05
  • Contact: HUANG Chong-Pin E-mail:huangcp@mail.buct.edu.cn

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摘要：

基于量子化学中的密度泛函理论(DFT), 研究了Beta分子筛中骨架Al在9个不同T位的分布和Brφnsted酸的分布及其强度. 计算采用8T 簇模型和B3LYP/6-31G(d,p)方法, 得到了不同T位的Al/Si替代能、(Al, H)/Si替代能和质子亲和势, 以及碱性探针分子NH3在Beta分子筛酸性位的吸附能. 结果表明, 骨架Al和Brφnsted酸优生位于Beta分子筛的T5 和T6 位; 其中酸性最强的位置是Al5-O14-Si9, 最弱的位置是Al7-O3-Si1.

关键词: Beta分子筛, Brφnsted酸, 密度泛函理论

Abstract:

Density functional theory (DFT) was applied to study the distribution of framework aluminum atoms at nine inequivalent T sites and the acidity of Brφnsted acid sites in Beta zeolite. The calculation was carried out at B3LYP/6-31G (d,p) level based on the 8Tclustermodel. According to the calculated Al/Si substitution energies, (Al, H)/Si substitution energies, proton affinities and the adsorption energies of ammonia (NH3), we propose that the most favorable sites for Al substitution and Brφnsted acid sites are at the T5 and T6 sites. The acidity of Al5-O14-Si9 is the highest among the preferred Brφnsted acid sites and the Al7-O3-Si1 site is the lowest.

Key words: Beta zeolite, Brφnsted acid, Density functional theory